Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758725AbYJPXX7 (ORCPT ); Thu, 16 Oct 2008 19:23:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757429AbYJPXXv (ORCPT ); Thu, 16 Oct 2008 19:23:51 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:52776 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757350AbYJPXXu (ORCPT ); Thu, 16 Oct 2008 19:23:50 -0400 Date: Thu, 16 Oct 2008 16:17:18 -0700 From: Andrew Morton To: David Brownell Cc: avorontsov@ru.mvista.com, linux-kernel@vger.kernel.org, stable@kernel.org Subject: Re: [patch] gpiolib: fix oops in gpio_get_value_cansleep() Message-Id: <20081016161718.e05864da.akpm@linux-foundation.org> In-Reply-To: <200810160845.22281.david-b@pacbell.net> References: <200810160845.22281.david-b@pacbell.net> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2131 Lines: 57 On Thu, 16 Oct 2008 08:45:22 -0700 David Brownell wrote: > From: David Brownell > > We can get the following oops from gpio_get_value_cansleep() > when a GPIO controller doesn't provide a get() callback: We can, but do we? ;) iow: is this needed in any -stable release? > Unable to handle kernel paging request for instruction fetch > Faulting instruction address: 0x00000000 > Oops: Kernel access of bad area, sig: 11 [#1] > [...] > NIP [00000000] 0x0 > LR [c0182fb0] gpio_get_value_cansleep+0x40/0x50 > Call Trace: > [c7b79e80] [c0183f28] gpio_value_show+0x5c/0x94 > [c7b79ea0] [c01a584c] dev_attr_show+0x30/0x7c > [c7b79eb0] [c00d6b48] fill_read_buffer+0x68/0xe0 > [c7b79ed0] [c00d6c54] sysfs_read_file+0x94/0xbc > [c7b79ef0] [c008f24c] vfs_read+0xb4/0x16c > [c7b79f10] [c008f580] sys_read+0x4c/0x90 > [c7b79f40] [c0013a14] ret_from_syscall+0x0/0x38 > > It's OK to request the value of *any* GPIO; most GPIOs are > bidirectional, so configuring them as outputs just enables an > output driver and doesn't disable the input logic. > > So the problem is that gpio_get_value_cansleep() isn't making > the same sanity check that gpio_get_value() does: making sure > this GPIO isn't one of the atypical "no input logic" cases. > > Reported-by: Anton Vorontsov > Signed-off-by: David Brownell > --- > drivers/gpio/gpiolib.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- a/drivers/gpio/gpiolib.c > +++ b/drivers/gpio/gpiolib.c > @@ -1056,7 +1056,7 @@ int gpio_get_value_cansleep(unsigned gpi > > might_sleep_if(extra_checks); > chip = gpio_to_chip(gpio); > - return chip->get(chip, gpio - chip->base); > + return chip->get ? chip->get(chip, gpio - chip->base) : 0; > } > EXPORT_SYMBOL_GPL(gpio_get_value_cansleep); > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/